Thanks for this. I really must dust that filter off and take it with me for the next shots where water is involved. It's easy to buy things and then kind of forget that you "really needed them". Reminds me of my sky tracker that wasn'tt very handy without a flip screen when I was using the 6D. An R changes that. No ND as of today but warmer temperatures ... maybe and not much snow.Jack -20°C here this morning, so I guess I can't complain, except we are going to get slammed with a massive snow storm tonight!
I bought the Canon PL-C52 (WII) several years ago and never used it until last year. For several years, I have been photographing this same pair of bald eagles along the Grand River. As you are probably quite aware, being a nature photographer you have to cooperate with mother nature. She provides the light often changing from one minute to the next. I use the polariser in situations where it is difficult to control the highlights, to reduce reflections in the water and to increase the blue colour tone in the sky. I use it with my Canon 200-400mm 1.4x and the 300mm 2.8.
Wanting to be more creative with my photography, I looked into buying ND filters but didn't want to pay the price...until the EOS R came out.
Hope the ND adapter arrives soon for you.